Bolt mechanism for an automatic firearm



Sept. 10, 1963 w. P. HIDDEN ETAL 3,103,142

l BOLT MECHANISM FOR AN AUTOMATIC FIREARM Filed Jan. 13. 1961 v 4 sheets-sheet 1 Sept. 10, 1963 w. P. HIDDEN ETAL 3,103,142

BOLT MECHANISM FOR AN AUTOMATIC FIREARM Filed Jan. 13, 1961 4 Sheets-Sheet 2 SePt- 10, 1963 w. P. HIDDEN ETAL 3,103,142

BOLT MEOHANISM FOR AN AUTOMATIC FIREARM l 4 Sheets-Sheet 5 Filed Jan. 13, 1961 Iva/Jef) -mvmw Sept` 10, 1963 w. P. HIDDEN ETAL 3,103,142

BOLT MECHANISM FOR AN AUTOMATIC FIREARM Filed Jan. 15, 1961 4 sheets-sheet 4 40 9846 V fog n2 72 99 82 ma JEL-Elfe innen United Sttes Patent O 3,103,142 BUL'I MECHANISM FR AN AUTUMA'IEC FlREAJRlt/l A Wiillam l?. Hidden, Wenham, Mass., Lawrence E. Steimen,"ll`opsheld, Mass., and Robert N. Sandberg, deceased, late of Beverly, Mass., by Sara F. Sandberg, administratrix,` Beverly, Mass., assignors, by mesure assignments, to the United States of America as represented bythe Secretary of the Army Filed lan. 13, 196i, Ser. No. 82,661 9 Claims. (ill. 89-18ti) This invention relates to automatic Aguns operated by recoil actuated barrels and more particularly to the bolt mechanisms therefor.

It is an object of this invention to provide for such automatic guns a bolt which is easily installed Within the receiver as it is unattached to any other member and lies on supporting slideways for free reciprocal flight.

It is another object of this invention to provide for such a boit la tiring pin which is seared by a rotary bolt lock to .assure positive locking of the bolt before the firing pin is released.

It is a further object of this invention to provide such a bolt lock which, during the rotation thereof to the unlock position, completes the retraction of the tiring pin to the cocked position and then retains it therein until the bolt is locked.

It is still another object of this invention to provide such a rotary bolt lock on which locking wings are eccentrically vdisposed so that the bolt is allowed to move rearwardly under blow back `forces during rotation of the bolt lock to the unlock position and thereby gradually break loose the tired cases from the barrel chamber to reduce the impact between the extractor claw and rim of the red cases when the bolt, after being unlocked, is accelerated to the recoil position.

It is another and `still further object of this invention to provide for such a bolt mechanism an accelerator which blocks the disengagement of the extractor from the eX- tractor grooves of the tired cases during initial extraction thereat from the gun barrel.

It is a further and still another object of this invention to provide in such a bolt mechanism a torsional type bolt return spring for greater eciency of the bolt mechanism and for facilitating the removal of the bolt from the gun receiver because this type of spring does not require the bolt to be `connected tol yany other member.

The specific nature of the invention as well as other objects and advantages thereof will clearly yappear from a description of a preferred embodiment as shown in the accompanying drawings in which:

FIG. 1 is a sectionalized elevational View of a gun with the bolt mechanism of this invention incorporated therein and shows the bolt `in recoil position;

FIG. 2 is a View taken along lline 2-2 of FIG. l;

FIG. 3 is a view taken along line 3 3 of FIG. l;

FIG. 4 is aview taken along line 4 4 of FIG. l;

FIG. 5 is a view taken along line 5 5 of FIG. l;

FIG. 6 is an enlarged longitudinally cross-sectioned side view of the gun showing the bolt adjacent recoil position during recoil flight;

FIG. 7 is a fragmentary view similar to FIG. 6 but showing the bolt locked in the battery position and the ring pin released;

FIG. 8 is a View taken along line 8 3 of FIG. 7;

FIG. 9 is 'a view taken along line 9--9 of FIG. 8;

FIG. 10 is a View similar to FIG. 8 but showing the cocking rotor engaged with the tiring pin and the barrel extension in its rearward position; and

FIG. L1 is a perspective View ofthebolt lock.

ICC

Shown rin the gures is a machine gun 12 provided with a rectangular receiver 14 which slidingly supports la barrel assembly 16 -having a barrel extension 18 with a barrel Ztl replaceably joined within the front end thereof for extension from the front end of the receiver.v The portion of barrel extension 18 which extends rearwardly from the breech of barrel 2li is bifurcated to form a right leg 22 yand a left leg '241 with an ejection passageway 26 therebetween to provide a clearance for the ejection of tired cases downwardly from the barrel and out the bottom of receiver 1li.

A back plate Z3 with a bolt buffer mechanism 30 contained therein is slidingly installed in the rear `end of receiver i4 by vertically disposed tongue and groove means. The distance between back plate Z8 and the front end of receiver 14 is sufficiently l,greater than the length of barrel extension 18 so that barrel assembly 16 may reciprocate therein, responsive to recoil forces produced by the discharge of Ia cartridge in barrel 20, to power gun 12 for automatic operation. A blind hole 31 extends forwardly into left leg 24 from the rear end thereof and such hole sliding receives a rod 32 which has contact with back plate 2S. A compressible coil spring 34 is disposed in hole 31 between the front end thereof and rod 32 so as to be enengized thereby during recoil movement of barrel assembly lr6 for returning the barrel assembly tothe forward position thereof. A spring-biased catch 35 is Iarranged in the left side of receiver 14 for re- Ileasable engagement with 'barrel extension 18 when in the forward position to retain the barrel extension therein. A plunger 33` extends slidingly through left leg 24 from ejection passageway 26 for registery with catch 35, as is best shown in FIG. 5, when barrel extension 18 is in the forward position, so that an inner displacement of the plunger will actuate the catch to an -unlatched position.

The top surfaces of right leg 22 and Ileft leg 24 are planarly formed and smoothly surfaced to provide slideways 36 for supporting a bolt 38 for reciprooation therealong between a recoil and a battery position.

Bolt 38 is Ireceived by ejection passageway Z6 and is provided with a right ilange 39 and a left flange 40 which extend laterally from respective sides of the bolt to` slidingly contact slideways 36 and thereby support the bolt for its reciprocation in the ejection passageway. The flanges 39" and 40 'are retained in contact with the slideways 36 by a feed tray 41 which is bingedly mounted on the top of receiver` 14 `and which is provided with a pair of rails 42. disposed along the underside .for sliding contact with the top of the flanges. A cover 37 is hingedly mounted on receiver 14- over feed tray 41 so that bolt 38 is easily installed Within the receiver after the cover and feed tray 41 are raised because by being unattached to any other member the bolt need only be laid upon slideways 36. A charging device (not shown) actuates bolt to the recoil position to be seared thereat as hereinafter described.

Catch '35 and plunger 33 are `disposed so as to be actuated by boltbiS when approaching the battery position to release barrel `assembly 16 from receiver 14 for recoil movement therein.

Bolt 38 carries, as will be explained in greater detail hereinafter, a rammer 43, an extractor 4d, a cocking rotor 46, a firing pin 43 and `a bolt lock 59. Rarnrner 43 is pivotally mounted onthe top of bolt 3S .for engagement with the cartridges successively indexed by a feeding mechanism S1 in a feed throat 552 of feed tray 41 for transferring the cartridges therefrom into the chamber of barrel 2li during the travel of the lbolt to battery position.

Extractor 44 is pivotally mounted on bolt 38 within an accommodating recess therein so that a claw 54 terminatin-g the front end of the extractor extends forwardly from the front face of the bolt for engagement with the extractor groove of the cartridge chambered in barrel 20 when the bolt goes into battery position. A ledge 56 (FIG. 6) is formed on the bottom of extractor 44 under claw 54 so -as to be exposed forwardly of the front face of bolt 38. A spring 58 is disposed between the bottom of extractor 44 and the ybottom of the laccommodating recess in the bolt for Ibiasing the extractor `upwardly to the cartridge engaging position. n

Firing pin 48 is slidingly mounted in bolt 38 by means Yofjarstepped recess 60 whichrpenrnits longitudinal reciprocation of the firing pin between a cocked andra firing position. Firing pin 48 includes a cylindrical spring housing 62, a rectangular body 64 which' extends integral-ly lforward from the front end thereof yand la cylindrical striker 66 whichis ixedly secured to the `body portion for longitudinal extension therefrom, As best shown in FIG. 6, housing 62 is provided with a cylindrical hole 68 which extends forwardly from the rear end thereof to a terminating wall 79 and such hole slidingly receives a sleeve 72 the rear end of which is closed by la base 73. A compressible coil spring 74 is disposed in sleeve 72 with the opposite ends having contact with ibase 73 and Wally 70 so that the spring is compressed therebetween when the ysleeve and housing 62 aretelescoped together.

The cross-sectional area of body 64 is smaller than that 'of housing62 so that a portion of the iront end thereof is exposed on opposite sides of the body and such exposed portion is contactable with a shoulder 75 in recess 60 when tiring pin 48 is in the ring position. The front end of housing 62 is `also contactable by cocking rotor 46, as hereinafter described, for initiating the displacement of iiring pin 48 to the cocked position. The front end of body 64 is recessed to form thereon an arcuate surface 76 (FIGS. 6 and 7) which extends rearwardly and downwardly from' the front end to the bottom of the ibody and which is contactable, as hereinafter described, by Ibolt lock 50 yfor holding the tiring pin 48 in the cocked position.

Firing pin 48 is secured within bolt 38 by a retainer 78 which is installed in the bolt by vertically disposed tongue and groove means in back of sleeve 72 after the sleeve is pressed forwardly -into housing 62 for preloading spring 74. A key 80 extending transversely across the bottom of recess 60 engages a keyway 81 in housing 62 for preventing rotational displacement of ling pin 48 while permitting longitudinal displacement thereof between the cocked and firing positions.

Bolt lock 50 is journaled in zbolt 38 :for rotation between a `lock and an unlock position by means of a bore `8?. which` extends laterally therethrough. Bore 82 is located so that surface 76 on firing pin 48 is disposedin the bore when the tiring pin is in the ring position and is also Idisposed so that theaxis thereof is located below the longitudinal yaxis of the firing pin and at right angles thereto.

Bolt lock 50, which is best shown in FIG. l1, includes a cylindrical -rnount 84 which is rotatingly received -by bore 82 and Iwhich has a length similar thereto. The ends of mount 84 are perpendicular to the longitudinal axis thereof and integrally extending from each of such ends is a wing 86. 'I'he wings 86 function, `as hereinafter described, to releasably lock bolt 38, When in the `battery position, to barrel extension 18.

Mount 84 is recessed Iby an arcuate channel 88 to provide a clearance for striker 66 during rotation 'between the lock and unlock positions. Channel 88 includes a front section 89 the longitudinal axis of which is disposed to that of the striker when the bolt lock is in the unlock position. Thus, front section 89 and rear section 91 are angularly related and converge at approximately the -center of bolt lock 50. Rear section 91 is enlarged to provide a pocket for receiving body 64 of firing pin 48 when the ring pin is in the tiring position. 90 includes a door surface 92, which is arranged so as to align with the bottom of body 64 when bolt lock Sti is nearly rotated to the lock position, and an end wall 94 which is disposed at right angles to the tloor and 1s spaced sutiiciently forward in mount 84 to permit unrestricted l displacementof ring pin 48 to the ring position. A

pair of camming surfaces 95 are formed on both .sides of rear section 91 of channel 88 eccentric to mount 84 asbest shown in FIG. ll. The intersection of loor'surface 92 -with the camming surfaces 95 `forms an interrupted sear edge 96 which is disposed, as shown in FIG. 7, so as to clear the bottom of body 64 for release of firing pin 48 just lbefore holt lock 58 reaches lock position during rotation thereto.

Cooking rotor 46 is mounted on Ibolt 38 between a pai-r of skirts 98 (FIG. 9) which extend laterally from left ange 40 and which Vare spaced vertically to permit insertion of the cooking rotor therebetween. A pin 99 extends vertically through rotor 46 and the skirts 98 to provide an axle for the rotation of the rotor. Rotor 46 includes a tang 109, which is contactable with the front end of housing 62, as `best shown in FIGS. 8 and l0, for displacing ring pin 48 suiiciently to move body 64 out of pocket 90 when the rotor is rotated. The yrotation of rotor'46 is achieved tby the successive engagements of a primary cog 182 and secondary cog 183 thereon with a cam surface 104 on the inside of the adjacent side of receiver 14 during initial movement of `bolt 38 from battery position. When ring pin 48 is retnacted by rotor 46, surface 76 on the front of body 64 is positioned for contact by the camming surfaces 95 on mount 84 when lbolt lock Si) is rotated from the lock position. Camming surfaces 95 `are so generated that the rotary contact thereof with surface 76 of firing pin 48 continues the retraction of the firing pin to the cocked position as the bolt lock completes its rotation to the unlock position.

The wings 86 are eccentrically disposed on the ends of mount 84 so that the undersides of the wings lie approximately along the diameter of the mount and, when Ibolt lock 50 is in the unlock position, the undersides are in alignment with the undersides of the respective ones of the flanges 39 and 4t), so fas to have sliding contact with the slideways 36, and the top sides of the wings are in longitudinal alignment with the top surfaces of the respective ones of the flanges 39 and 40 and are disposed for sliding contact with the rails 42. Each of the `wings 86 is provided at the rear end with a locking surface 106 which lis angularly ldisposed relative -to the longitudinal axis of the associated Wing so as to be substantially vertically disposed as shown in FIG. 9 when bolt lock Sti is in the is mounted on right leg 22 of barrel extension 18 at the j front end of the slideway 36 thereon so that a cam surf yface on the rear end of the cam block is engaged by the front end of the right one of the wings 86 when bolt 38 is adjacent battery position.

A plunger 112 is mounted on the inside of receiver v14 so as to be partially received in a notch 109 in the left one of the wings 86 immediately before the right one of the wings conta-cts cam surface 110 for locking bolt lock in the lock position. Plunger `112 is biased rearwardly -b-y a spring 1113 whereby, when the right one of the wings 86 contacts cam surface 110 and initiates the rotation of of bolt lock 50 to -the lock position, such spring is compressed. Provided on ythe rear end of plunger 112 is a cam surface l115 ywhich extends upwardly and forwardly Pocket therefrom and which is disposed for engagement with the bottom front corner of the left one of the wings 86 after rotation of bolt lock is initiated by cam surface 11i). The bias of cam surface 115 and the tension 4of loaded spring 113 completes the rotation of bolt lock 50 to the lock position. The shape of cam surface 111i is generated to accelerate bolt lock 511 to an angular velocity which is appreciably greater than and proportional to the linear velocity of bolt 38 so that, no matter how high the bolt velocity is, it is impossible for the bolt to bounce out of battery position before the bolt lock reaches the lock position.

When bolt lock 5t) is rotated to the lock position, wherein the wings 86 are angularly disposed relative to the longitudinal anis of bolt 38, the locking surfaces 106 are received by V-shaped recesses 114 formed in the slideways y36. The rear sides of the recesses 114 form engaging surfaces y116 which, as shown in FIG. 9, are so angularly disposed that, when the` locking surfaces `106 are pressed rearward therea-gainst by the rearward pressure applied to bolt 33 through the discharge of a cartridge in barrel 20, bolt look 56' is energized in the direction of locking and thereby positively locks the bolt in the battery position. Bolt lock 511 is actuated to the unlock position by cam surfaces 118 which terminate respectively at the lfront ends .of the rails 42 and which are disposed so -that bolt 33 is unlocked from barrel assembly 16, during recoil travel thereof, when the gas pressure in barrel 20 is reduced to safe limits.

The recoil energy in barrel assembly 16 is transferred to bolt 38 for reciprocation to and from the recoil position by accelerator devicel 121B` which is mounted within receiver 14 under barrel extension 1S. Accelerator device 129 includes a rectangular housing 122 which is located at the rear end of receiver 14 and which is slidingly mounted therein on longitudinally kdisposed tongue and groove means 121 (FIG. l). Housing 1212 is backed up by back plate 2S. A tubular `casing 124 (FIG. l) extends forwardly from housing 122 along the right side of the receiver and such casing is provided with a longitudinal bore 126 which extends rearwardly `from the front end and which is counterbored from the front end, as noted at 123, to form an annular shoulder 130. A buffer device 132 is installed in countenbore 123 and such device includes a cylindrical head 134 having approximately the same diameter as the countenbore so as to be slidingly received thereby. An annular flange 135 around the front end of head 134 limits the movement thereof into counterbore 1128. A rod 136 extends axially from head 134 into counterbore 128 and slidingly mounted thereon is a washer 133 whichis backed by a nut 140 threaded to the end ofthe rod. A compressible coil spring 142 is disposed on rod 136 between head 134 and` washer 138 and is preloaded by tightening nut 140 against the washer. When buffer device 132 -is installed in coun-v of a pin 145 which extends transversely through the lever approximately midway of the top` and bottom thereof. An arm 146 extends laterally from the bottom of vaccelerator lever 144 for contact with the front end of shaft 143 duri-ng recoil movement of barrel extension 18. The top portion of accelerator lever 144 includes a -pair of laterally spaced fingers 148 which contact the fron-t face of bolt 38 on opposite sides of extractor 44. When bolt 33 is locked to barrel extension 18 during initial recoil movement thereof, accelerator lever 144 is prevented from pivotal movement whereby the rearward movement of the barrel extension is transferred to buffer device 132 to press head 134 resiliently into counterbore 128. Consequently, when bolt 33 is unlocked from barrel exten-sion 18 and accelerator lever 144 is free to pivot, the resiliency of the loaded spring 142 acting against the accelerator lever propels the bolt rearwardly at an accelerated Velocity. Provided on the inside of each of the ngers 148 is a lug 149 (FIGS. 4 and 5) which is contactable by ledge 5 6 of extractor 44 to prevent disengagement of claw 54 yfrom the extractor groove of a tired case during initial extraction from barrel 21B.

When bolt 38 goes into recoil position, sufiicient energy 1211 is disposed for resilient forward movement in receiver `14, theishock of impact between latch 152and bolt 33 is cushioned by accelerator bulfer device 132.

vBolt return spring mechanism 151i` includes a cage 154 which is slidingly installed in receiver 114 above barrel extension 1S on longitudinally disposed tongue and groove means and is secured in position by back plate 28. Cage 154 includes a pair of laterally spaced flanges `156 which terbore 128, washer `138 contacts shoulder 130 therein and the length of rod 136 is arranged so that flange 135 is spaced from the `end of casing 124 to permit resilient.

. against the bias of spring 142 to telescope casing 124 over the head 134.

A sha-ft 143 (FIG. l) extends axially forward lfrom head 134 for engagement by an accelerator lever 144 which is pivotally mounted on barrel extension 18 in the front end of ejection passageway 26. Accelerator lever 144 is pivotally'mounted on barrel extension 18 by means extend rearwardly from an inverted U-shaped, crossasup- `port 157 and which support therebetween a laterally disposed rod 158. Rod 158 is inserted through the coils of a pair of double-armed springs 16()y having outside arms 162, which are curved to contact the top of cross-support 157, and inside arms V1164, which have contact with the rear side of a cross-piece 166 extending across the underlside of cross-support 157 so that such inner arms may be actuated rearwardly to Wind the springs. The ends of the inside arms 164 extend forwardly and then outwardly `so as to be contactable by the rear end of bolt 313 when adjacent recoil position for winding the springs 1611 and transfer thereto sufficient energy for returning the bolt to battery position. Latch 152 is disposed so as to engage stop 153 to hold bolt 38 in the recoil position, when the springs 163 are wound, whereby, the bolt is propelled ,by the springs to the battery position when released by latch 152.

Operation Gun `12 is fired from the open bolt position, with bolt 38 seared in recoil position by latch 152, so that a cartridge is never retained in a hot chamber to create a ,coolooi hazard between bursts. A burst is initiated by actuating latch 152 to release bolt 38 which, when released, is propelled in -free iiight to battery position v through the energy transferred to bolt return springs 160 tained in the unlock position during such ilight through i the sliding contact of the wings S6 between rails 42 and slideways 36.

`When bolt `33 is adjacent battery posit-ion, plunger 33 is contacted thereby to actuate catch 35 for release of barrel assembly 16 from receiver 14 so that it is free for recoil displacement when the chambered cartridge is discharged. At approximately the same time, plunger 1:12 is contacted by the left one of the wings 86 and is pressed forwardly to load spring 113 and apply the energy in the spring under the front end of such wing. T he right one of the wings 86 then contacts cam surface 116 of cam block 108 to initiate the rotation of bolt lock 50 from the unlock to the lock position. Plunger 112 continues the rotation of bolt lock 50 until locking surfaces 166 thereon are in full Contact with engaging -surfaces 116. Because of the rearward bias of plunger 112 and the engagement thereof with notch 109 in the left wing 86, bolt lock 5G is securedl against displacement from the lock position.

At a point where bolt lock Si) has rotated to a safely locked position, but before it has reached full rotation, c

sear edge 96 on the bolt lock clears the bottom of body 64 of ring pin 48 which is freed thereby to be driven forwardly by spring 74 to strike the primer of the chambered cartridge for discharge thereof. Boltlock 50 continues to locked position as firing pin 48 goes forward to discharge the chambered cartridge.

Upon the discharge of the chambered cartridge, barrel assembly 16, previously unlocked from receiver 14, 'is energized for rearward movement in the receiver against the resistance of spring 34 to carry with it bolt 38 which is locked by bolt lock 50 to barrel extension 18. As bolt 38 is prevented from movement relative to barrel assembly 16, accelerator. lever 144 is held against pivotal displacement and, therefore, the rearward movement of the accelerator lever with thev barrel assembly is transferred to buffer device 132 to load spring -142 therein.

While accelerator lever 144 is in contact with the locked bolt 3S, it is held in the upright position so that the lugs 149 thereon are disposed under ledge y56 of extractor 44 to block the disengagement of claw 54 from the extractor groove of the ired cartridge case to assure positive extraction thereof. l f

During the initial recoil movement of barrel assembly 16, cog 102 of cocking rotor 46 contacts cam surface 104,-

v-to rotate the cocking rotor.

Whereby, tang 100 is ac tuated against the front end of housing 62 to retract firing pin 48 sufficiently for striker 66 to be extracted from the primer of the red cartridge case and for body 64 to be clear of pocket 90 in bolt lock 50. Also, duning l initial recoil movement of barrel assembly y16, lockingv plunger 112 contacts an abutment `170 (FIG. 8) fixed to receiver 14 which causes the cocking plunger to become disengaged from notch 109 in the lower surface ofthe left one of wings 86 of bolt lock 50i. Thus, bolt lock 5t) is free for rotation when the top front ends` of the wings 86 contact the cam surfaces 1'18 on rails 42. When the wings 86 contact cam surfaces 1'18, bolt lock 59 is rotated to the unlockvposition, with camming surfaces 95 on mount 84 rotatingly engaging surface76 at the front end of firing pin body 64 to complete the retraction A of firing pin 48 to the cocked position during the rotation of the bolt lock to the unlock position. Because of the eccentric mounting of the wings 86 on mount 84, when 16, the loaded accelerator buffer device 132 acts topivot acceleratork lever 144 against the front end of the bolt 8 bottom of receiver 14. In the meantime, the recoil energy in barrel assembly 16 is absorbed by spring 34 which uses the transferred energy to return the barrel assembly to the forward position wherein it is -secured by catch 35.

When bolt 38 is adjacent recoil position in its 4rear- From the foregoing'it is clearly apparent that there is Y provided herein a bolt which, among `its many advantages, is easily removed from the receiver by raising the cover and feed tray as it is unattached to any other member. Furthermore, r-ing before the bolt is locked is prevented by the ring pin being seared by the bolt lock which cooperates with a cooking rotor in retracting the firing pin to the cocked position. Extraction of the ring case, too, is facilitated through the rearward displacement ofthe lbolt by the bolt lock dur-ing unlocking and having the extractor blocked in engagement with the extractor groove -of the fired case by the accelerator. Moreover, the bolt return spring is of torsional type which has a greater efficiency than the conventional helical types. The bolt mechanism is also distinguished for its rugged con struction, ease of manufacture and positive operation.

Although a particular embodiment of the invention has been described in detail herein, it is evident that many variations may be devised within the spirit and scope thereof and the following claims are intended yto include such variations.

We cla-im: l. A bolt mechanism for a iirearm having a receiver and `a `barrel' assembly including a barrel and a vbarrel extension disposed in the receiver for reciprocation rebarrel extension, an engaging surface formed in each one `of said recesses for contact by the related one of said locking surfaces when said bolt lock is in the lock position to block rear displacement of said bolt from battery position, said wings beingy so` eccentrically disposed on said mount and said locking surface being so related to said engaging surfaces that gradual rearward displacel ment `of said bolt relative to said barrel is permitted during rotation `of said barrel lock from the locked position to an unlocked position, a firing pin slidingly disposed in' said bolt and biased therein yfrom a cocked to a firing to catapult the bolt rearwardly in free night to the recoil position carrying with it the fired case which, when con-v tacted by an ejector 1168 depending from feed tray 41, is ejected through ejection passageway 26 and out the position, said firing pin including a'rectangular body, a striker extending forwardly therefrom, an arcuate surface formed in the front end of said body, a recess arranged in said mount for receiving said striker so as to permit rotation of said bolt lock between the lock and unlock position, `a pair of camming surfaces formed on opposite sides of smid recess so as to cooperate with said arcuate surface ion said firing pin body when engaged therewith for icompleting the retraction of said firing pin to the cocked position when said bolt lock is rotated to the unlock position, a pocketformed at the rear' endof said recess for receiving said body to permit the displacement' of said ring pin from the cocked to the firing position,

and a sear edge formed =at the junction of said pocket' and said camming surfaces, said sear edge being disposed to release said firing pin for discharge of the cartridge in Ithe barrel lwhen said wings are positioned suflicien-tly 9 within said recesses to block rearward displacement of said bolt during rotation of said bolt lock to the lock position.

2. The ybolt mechanism as defined in claim 1 and including a cocking rotor mounted on said bolt by means of a vertical-1y disposed axle pin, a cog extending from said rotor for engagement by a cam surface on the receiver during initial rearward :displacement of said bolt with the barrel assembly for rotating said rotor, and a tang extending from said rotor for engagement with said firing pin during lrotation of said rotor for displacing said firing pin `sufficiently to retract said body from said pocket and position said arcuate surface on said body for engagement by the camming surface of said mount when said bolt lock is rotated from fthe lock position.

3. A bolt mechanism for a firearm having a receiver with a cover and a feed tray hingedly mounted on the top of the receiver to uncover the top thereof when the cover and feeditray are swung open and a barrel assembly with a barrel extension and barrel disposed for longitudinal reciprocation in the receiver between a rear and a forward position responsive to energy transferred to the barrel assembly from the explosion of a cartridge in the barrel, the barrel extension -being provided with a left leg and a right leg and a passageway formed therebetween, the bolt mechanism including a bolt slidingly received in the passageway, a pair of flanges extending from opposite sides of said bolt for sliding cont-act with the tops of the right and left legs to slidingly support said bolt for reciprocation between a battery and a recoil position and permit assembly of said fbolt to the barrel extension from the top of the receiver when the cover and feed tray are open, 'a pair of rails depending from the feed tr-ay for sliding `contact with thetops of said flanges when the feed tray is closed to the receiver to prevent angular displacement of said bolt in its reciprocation, locking means rotatingly disposed in said bolt for latching said bolt when in its battery position to the barrel extension for rearward movement therewith, means for unlatching said bolt from the barrel extension when the bar-rel assembly is adjacent the rear position thereof, an accelerator device energized by the barrel assembly during displacement thereof to the rear position, means for transferring the energy stored .in said accelerator device to said bolt after being unlocked from the barrel extension for catapulting said -bolt in free flight to the recoil position, and a bolt return spring device mounted on the rear end of the receiver so las to be contacted by said bolt when adjacent .the recoil position for propelling said bolt in free flight to the battery position and energized.

4. The bolt mechanism as defined in claim 3 wherein said bolt return spring device includes a torsional spring which is disposed for engagement by said bolt when adjacent recoil position so as to be energized thereby vfor propelling said bolt to the battery position.

5. The bolt mechanism as defined in claim 3 wherein said bolt return spring device includes a cage, a -laterally disposed rod supported by said cage, a pair of torsional springs coiled aronnd said rod, each of said torsional springs having an inner arm contactable by said bolt when adjacent the recoil position for moving said inner arm in a winding direction and an .outer arm anchored to said cage so that the winding ydisplacement of said inner arm energizes the related :one .of said springs.

6. The bolt mechanism as Idefined in claim 3 wherein said accelerator device includes a casing longitudinally mounted in the receiver at one side thereof, said casing being provide-d with a longitudinal bore counterbored at the front end to form an annular shoulder in said casing, a butter device received by said counterbore, said butter device including a spring buttressed by said shoulder, a head slidingly received by the front end of said counterbore for contact with lthe front end of said spring so as to compress said spring when moved rearwardly thereagainst and a rod extending forwardly from said head, and an accelerator lever mounted in the barrel extension in the ejection passageway by means of a transversal pin extending through said accelerator lever intermediate the top 'and bottom thereof, said accelerator lever being contactable abo-ve said pin with the front face of said bolt, and an arm extending laterally from said accelerator lever below said pin for contact with the front end of said buifer rod, whereby when said bolt is latched to the barrel extension and the barrel assembly is actuated rearwardly the rearward movement thereof is transferred to said rod for compressing said spring so that said accelerator lever is energized thereby for catapulting said bolt to the recoil position when unlatched from the barrel extension.

7. The bolt mechanism as defined in claim 3 wherein said accelerator device includes a housing slidingly disposed in the receiver on longitudinally disposed tongue and ygroove means, a latch pivotally mounted on the top of said housing for releasable engagement with said bolt to sear said bol-t in the recoil position, a casing extending integrally forward from said housing along the right side of the receiver, said casing being provided with a longitudinal bore counterbored `from the front end to form an annular shoulder in said casing, -a lbuffer device disposed within said counterbore, said buffer device including a spring buttressed by said shoulder and a head slidingly received by the front end lof said counterbore for limited rearward displacement into said counterbore to compress said spring, a lug extending inwardly from the receiver for contact with the front end of said fhead whereby said spring is compressed during forward displacement of said accelerator for cushioning the impact of engagement between said latch and said bolt, and an accelerator lever pivotally mounted in said barrel extension and operationally interposed between said buifer device and said bolt for loading said spring during rearward displacement of said barrel assembly to propel said bolt to the recoil position after ibeing unlatched therefrom.

8. The bolt mechanism as defined in claim 3 wherein said bolt is provided with a spring-biased extractor having a claw which is disposed forwardly of the front face of said bolt for engagement with an extractor groove of the cartridge chambered in the barrel and a ledge disposed under said claw and forwardly of the front face of said bolt, and wherein said accelerator device is provided with means forblocking disengagement of said claw from the extractor groove while said bolt is latched to the barrel extension.

9. The bolt mechanism as defined in claim 8 wherein said accelerator device includes an accelerator lever mounted ion the barrel extension within the ejection passageway on a transversal pin extending through said accelerator lever intermediate the top and bottom thereof, said accelerator lever having a pair of fingers which are disposed above said pin for contact with the front face of said bolt on opposite sides `of said extractor, and lugs extending from said lingers under said extractor for contact with said ledge when said bolt is latched to the barrel extension for blocking the displacement of said claw from engagement with the extractor groove of the cartridge.

References Cited in the file of this patent 'UNITED srArEs PATENTS 1,985,493 Gebauer et al Deo. 25, 1934 2,491,539 Windham Dec. 20, 1949 2,512,027 Lippert et al. lune 20, 1950 2,600,007 Lippert June 10, 1952 2,973,693 Colby Mar. 7, 1961 

1. A BOLT MECHANISM FOR A FIREARM HAVING A RECEIVER AND A BARREL ASSEMBLY INCLUDING A BARREL AND A BARREL EXTENSION DISPOSED IN THE RECEIVER FOR RECIPROCATION RESPONSIVE TO FORCES PRODUCED BY THE DISCHARGE OF A CARTRIDGE IN THE BARREL, THE BOLT MECHANISM INCLUDING A BOLT DISPOSED FOR FREE RECIPROCAL FLIGHT ON THE BARREL EXTENSION, A ROTARY BOLT LOCK INCLUDING A CYLINDRICAL MOUNT JOURNALED IN A BORE EXTENDING LATERALLY THROUGH SAID BOLT, A WING ECCENTRICALLY DISPOSED ON EACH END OF SAID MOUNT AND A LOCKING SURFACE DISPOSED ON THE REAR END OF EACH OF SAID WINGS SO AS TO BE RESPECTIVELY RECEIVED BY A RECESS IN THE BARREL EXTENSION, AN ENGAGING SURFACE FORMED IN EACH ONE OF SAID RECESSES FOR CONTACT BY THE RELATED ONE OF SAID LOCKING SURFACES WHEN SAID BOLT LOCK IS IN THE LOCK POSITION TO BLOCK REAR DISPLACEMENT OF SAID BOLT FROM BATTERY POSITION, SAID WINGS BEING SO ECCENTRICALLY DISPOSED ON SAID MOUNT AND SAID LOCKING SURFACE BEING SO RELATED TO SAID ENGAGING SURFACES THAT GRADUAL REARWARD DISPLACEMENT OF SAID BOLT RELATIVE TO SAID BARREL IS PERMITTED DURING ROTATION OF SAID BARREL LOCK FROM THE LOCKED POSITION TO AN UNLOCKED POSITION, A FIRING PIN SLIDINGLY DISPOSED IN SAID BOLT AND BIASED THEREIN FROM A COCKED TO A FIRING 